>I would guess this is a mission and not just training activity. Guess only.
I'd guess training (guess only also) …using training callsign & last day of the month, last day of the quarter, and last day of the semi-annual training periods, so LAST CHANCE to complete their training requirements
If they don't complete the requisite number of training events within the designated timeframe (month/quarter/semiannual/annual) then they have to fly remedial training under supervision of an instructor (like getting your drivers license rescinded and handed a learners permit!)